Normal, non-specifically and specifically immune macrophages in the presence of specific T. cruzi antibody will be studied with regard to how they cope with each morphogenetic form of the parasite. The manner by which macrophages deal with these intra-cellular parasites will be studied by electron microscopy. The isolation, purification and infectivity of each form of T. cruzi will be evaluated. In vivo studies are to be done in order to determine the effect of cell transfer, antibody, antibody with activated macrophages, and sensitized lymphocytes on experimental infection. Finally, non-living antigens will be prepared using procedures as acetoacetylation, periodation and solubilization in order to assess their suitability as protective antigens.